1. Field of the Invention
The present invention relates to an inkjet printer having a bi-directional print function, and more particularly, to a print control apparatus and a method for inkjet printers capable of preventing print quality deterioration due to print position errors when bi-directional print operations are performed.
2. Description of the Related Art
Typically, inkjet printers use a micro injecting device with an ink cartridge. The micro injecting device is used often due to its color print implementation, less noise, and gorgeous print quality. The inkjet printers fire ink through nozzles of the micro injecting device to perform print jobs and are provided with an encoder sensor to sense the location of a carriage mounted in the micro injecting device as well as to control the speed of the carriage via a print control signal.
FIG. 1 is a block diagram illustrating an example of a print control apparatus for a conventional inkjet printer.
Referring to FIG. 1, a print control apparatus has an encoder strip 10, an encoder sensor 20, a position counter 30, a register 40, a comparator 50, and a controller 60.
The encoder strip 10 has slits spaced in certain intervals and formed on one side thereof.
The encoder sensor 20 is disposed in proximity to the encoder strip 10, and outputs a pulse signal according to the slits formed on the encoder strip 10. That is, the encoder sensor 20 emits light onto the encoder strip 10, receives light passing through the encoder strip 10, and outputs two-phase signals CHX and CHY. The two-phase signals CHX and CHY are used to control the travel direction and speed of the carriage return motor.
The position counter 30 increases or decreases a certain counting value in relation to the level changes of the two-phase signals CHX and CHY output from the encoder sensor 20.
The comparator 50 compares a position value counted by the position counter 30 and a reference position value pre-stored in the register 40, and outputs a comparison result signal to the controller 60.
If the position value counted by the position counter 30 is determined to be identical to the reference position value pre-stored in the register 40 as a result of the comparison of the comparator 50, the controller 60 recognizes that the carriage is trying to get to a print start position. If the carriage is determined to be trying to get to the print start position, the controller 60 generates a print reference signal based on the rising edge or the falling edge of a reference signal, such as a signal CHX, of the two-phase signals CHX and CHY output from the encoder sensor 20, and outputs the print reference signal to a printer head (not shown). The print reference signal indicates a signal having all the nozzles of the printer head fired.
Descriptions will be made, for example, where a print reference signal is generated based on the rising edge of a first signal CHX which becomes a reference signal of the two-phase signals CHX and CHY output from the encoder sensor 20.
When the carriage is determined to be traveling from left to right or from right to left, the controller 60 generates a print reference signal based on the rising edge of the first signal CHX output from the encoder sensor 20.
As mentioned above, in case the controller 60 generates the print reference signal based on the rising edge of the first signal CHX output from the encoder sensor 20 regardless of the travel direction of the carriage, as shown in FIG. 2, a problem occurs where the print start positions are not aligned due to print position errors.
In FIG. 2, a reference numeral ‘A’ denotes print positions where, when the carriage travels from left to right, the controller 60 performs a print job based on the rising edge of the first signal CHX output from the encoder sensor 20, and a reference numeral ‘B’ denotes print positions where one period of the first signal CHX is divided into a half thereof.
A reference numeral ‘A’ denotes print positions where, when the carriage travels from right to left, the controller 60 performs a print job based on the rising edge of the first signal CHX output from the encoder sensor 20, and a reference numeral ‘B′’ denotes print positions where one period of the first signal CHX is divided into a half thereof.
As shown in FIG. 2, if a print job is performed with reference to the positions A and A′, it is possible to print with a higher resolution than a resolution of the encoder strip 10, and, if a print job is performed with reference to the positions B and B′, it is possible to print with a higher resolution than a resolution of the encoder strip 10. As such, if a print job is performed with a one-period signal of the encoder sensor 20 being divided into a certain period, high resolution printing becomes possible with the encoder strip 10 of low resolution. Furthermore, in case a bi-directional print job is performed, high resolution printing becomes possible.
However, if the print reference signal is output based on a different edge when the bi-directional print job is performed as in the prior art, an error occurs during a certain interval C, as shown in FIG. 2, at print positions due to the tolerance of slits formed on the encoder strip 10. Accordingly, a problem occurs that deteriorates the print quality since print start positions are not aligned.